With contemporary operating systems, such as Microsoft Corporation's Windows® XP operating system with an underlying file system such as the Windows® NTFS (Windows® NT File System), FAT, CDFS, SMB redirector file system, or WebDav file systems, one or more file system filter drivers may be inserted between the I/O manager that receives user I/O requests and the file system driver. In general, filter drivers (sometimes referred to herein simply as “filters”) are processes or components that enhance the underlying file system by performing various file-related computing tasks that users desire, including tasks such as passing file system I/O (requests and data) through anti-virus software, file system quota providers, file replicators, and encryption/compression products.
For example, antivirus products provide a filter that watches I/O to and from certain file types (.exe, .doc, and the like) looking for virus signatures, while file replication products perform file system-level mirroring. Other types of file system filter drivers are directed to system restoration (which backs up system files when changes are about to be made so that the user can return to the original state), disk quota enforcement, backup of open files, undeletion of deleted files, encryption of files, and so forth. Thus, by installing file system filter drivers, computer users can select the file system features they want and need, in a manner that enables upgrades, replacement, insertion, and removal of the components without changing the actual operating system or file system driver code.
A file system filter may maintain internal metadata for files and directories on a volume. Changes to a volume that a filter is associated with may cause the internal metadata of the filter to be out of sync with the state of the volume. This may cause the filter to behave incorrectly or render it unable to perform its desired function.
What is needed is a method and system for maintaining consistency between the namespaces of selected objects maintained by a file system and a filter associated therewith.